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Archive for Thursday, September 9, 1999

CAR TALK

September 9, 1999

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Dear Tom and Ray:

Is it better to apply the brakes and then let off alternately, or just apply steady pressure when slowing down or stopping? And which method causes less wear on the brakes? -- Bishop

RAY: Well, let's ignore the wear-and-tear issue for the moment. There are a couple of safety situations that call for "alternating on and off" the brakes. One is slick roads. If you don't have anti-lock brakes, pumping the brakes (releasing them just as they start to lock up and then immediately reapplying them) can help you stay in control of the car and keep from skidding while you stop.

TOM: The other situation where constant, steady pressure is NOT a good idea is when you're going down a long, steep hill. Then you want to use a low gear AND minimize your dependence on the brakes. Excessive use of the brakes -- whether constant or intermittent -- could lead the brakes to overheat, which could make the brake fluid boil and lead to complete brake failure.

RAY: But to get back to your question about which method causes less wear on the brakes, the answer is: Nobody knows. And my guess is that -- in terms of wear and tear on the brakes -- the difference is so slight that it hardly matters.

TOM: However, I'd strongly recommend against "pulsing" the brakes under normal circumstances. Even if it does cause less wear and tear (and that's a big "if"), any money you save will be more than eaten up by the cleaning bills -- the bills to remove the puke stains from the upholstery from all of your nauseated passengers. So except in the situations we mentioned above, Bishop, try to brake smoothly and gently.

Dear Tom and Ray:

I have a 1991 Buick Custom Century with only 19,900 miles on it. I'm getting a loud "thump, thump, thump" every time I make a right turn. I took it to our local Buick dealer, and he sent a mechanic out with it; when he came back, the head mechanic went out with it. When he came back, he said my car was out of line and said to get the wheels aligned and get new tires because they were cupped. I did all he said, but now I still get the "thump, thump, thump." I have had the front brakes renewed, and it's still there. I had a new muffler system put in, and still the thump. I have spent more than $600, and it's still "thump, thump, thump" on right turns. What gives? -- William

RAY: I don't think your car was "out of line," William. I think it was your dealer who was out of line.

TOM: Your tires may, in fact, have been cupped, but I'm pretty sure your problem is a bad constant-velocity (CV) joint. CV joints are complex universal joints on the front axles that allow the front wheels to both move up and down AND left and right to steer the car. And the thumping or clacking you hear on turns is a classic symptom of a bad CV joint. Classic! Right out of the textbook.

RAY: So ask a mechanic you trust to check out your CV joints, William. Three hours and $300 later, I'll bet your "thump, thump, thump" is ancient history.

Dear Tom and Ray:

I have a 1987 Toyota Supra that I love dearly. For the past year or so, every time I go to the post office, it won't restart. If I shift it back and forth between Neutral and Park, it finally starts in one of those positions. I thought it was the battery, because I used to get out and bang on the battery cables and that sometimes worked. I can't believe this car is smart enough to know when it's at the post office. My mechanic said that unless it was doing it for him, all he could do was start replacing parts. -- Jan

RAY: Well, that's one way of going about it, Jan. Unfortunately, both of the suspect parts in this case are rather pricey.

TOM: I would suspect either the starter or the Neutral Safety Switch. The Neutral Safety Switch prevents you from starting the car unless the transmission is in either Park or Neutral. Why? So you don't accidentally start the car in Drive and plow into the "Stamped Mail" collection box.

RAY: And if the Neutral Safety Switch is on the fritz and working intermittently, it could be causing your problem.

TOM: Unfortunately, the Neutral Safety Switch in this car is part of the backup-light control unit, and the part costs about 250 bucks. So I wouldn't just throw one in unless you have 300-plus bucks to fritter away (which we know you don't, otherwise, you wouldn't be driving an '87 Toyota).

RAY: So if you can't get it to fail for your mechanic, I'd ask him to lend you a test light and show you how to use it. It's pretty easy.

TOM: Then, next time you go to mail a letter and the car won't start, you hook up the test light to the starter solenoid wire. Then you ask Newman (or the nearest letter carrier) to turn the key for you. If the test light lights up and the car doesn't start, then you know the Neutral Safety Switch is working, because power is getting past it and to the starter. If the light stays dark, then you know the Neutral Safety Switch is not letting any power through and needs to be replaced.

RAY: Why does it only happen at the post office? I suspect it's related to the post office's distance from your house, and how long you drive the car before shutting it off and trying to restart it. That affects how hot things get, and that's why it happens at the post office and not first thing in the morning or after work when the engine is cold.

TOM: Or your car may be like my dog and just have an innate dislike for letter carriers.

  • Have a question about cars? Write to Click and Clack in care of the Journal-World, 609 N.H. 66047 or e-mail them by visiting the Car Talk section of cars.com on the World Wide Web.
  • Car Talk with Click and Clack airs at 9 a.m. Saturdays on KANU-FM 91.5.

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